The present invention relates generally to telecommunications, and in particular to apparatus and methods to facilitate testing of POTS service.
A variety of telecommunication systems utilize traditional telephone company local subscriber loops to carry high rate digital transmissions. Examples include a variety of digital subscriber loop (DSL) services, such as high-rate DSL (HDSL), asymmetric DSL (ADSL), very high-rate DSL (VDSL) and others. The varieties of DSL service will be referred to herein generally as xDSL. The xDSL services share the same carrier with traditional analog telephony, commonly referred to as plain old telephone service (POTS).
With the growth of the xDSL for digital and voice service, a robust line test system is required for maintenance facilities and troubleshooting without interrupting services. When a conventional butt-in test set is switched xe2x80x9coff-hookxe2x80x9d to test the POTS service on a shared line, the test set can create an impedance change on the subscriber line that interferes with the data signal.
For the reasons stated above, and for other reasons stated below that will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for alternative apparatus and methods to facilitate testing of POTS service in a shared POTS/xDSL system.
The various embodiments include microfilters that are selectively coupled to a carrier in a shared POTS/xDSL system on the subscriber loop side of an xDSL filter associated with a subscriber line interface circuit. The various embodiments facilitate testing of the POTS service using an insertion point that is between the xDSL filter and the subscriber loop in a manner that is transparent to subscribers.
For one embodiment, the invention provides a system for testing POTS service on a line shared with xDSL service. The system includes a first microfilter selectively coupled to an xDSL filter on the line through a first relay. The system further includes a second microfilter selectively coupled to the line through a second relay. The first and second relays are on a subscriber loop side of the xDSL filter. The subscriber loop is decoupled from the xDSL filter when the first microfilter is coupled to the xDSL filter and the subscriber loop can remain coupled to the xDSL filter when the second microfilter is coupled to the line.
For another embodiment, the invention provides a telecommunications system. The telecommunications system includes a subscriber line interface circuit, an xDSL transceiver, an xDSL filter coupled between the xDSL transceiver and the subscriber line interface circuit, and a communication line coupling the subscriber line interface circuit and the xDSL transceiver to a load. The telecommunications system further includes a first relay on the communication line between the xDSL filter and the load, a second relay on the communication line between the xDSL filter and the load, a third relay on the communication line between the xDSL filter and the load, a first microfilter coupled to the first relay and a second microfilter coupled to the second relay. The first microfilter is selectively coupled to the subscriber line interface circuit through the first relay and the first relay decouples the load from the subscriber line interface circuit when the first microfilter is coupled to the subscriber line interface circuit. The second microfilter is selectively coupled to the communication line through the second relay, but the second relay does not decouple the load from the subscriber line interface circuit when the second microfilter is coupled to the communication line. The third relay selectively decouples the load from the subscriber line interface circuit for coupling the load to a test port.
For yet another embodiment, the invention provides a method of testing POTS service on a line shared with xDSL service. The method includes coupling a test-in port of a metallic loop test set to a first microfilter and coupling the first microfilter to a subscriber line interface circuit at a point located on a subscriber loop side of an xDSL filter associated with the subscriber loop interface circuit. For a further embodiment, the method further includes coupling a test-out port of the metallic loop test set to a second microfilter, coupling the second microfilter to a subscriber load on the subscriber loop side and detecting whether there is voice traffic on the subscriber loop. For a still further embodiment, the method further includes coupling the test-out port of the metallic loop test set to the subscriber load, bypassing the second microfilter, if no voice traffic is detected on the subscriber loop.
For another embodiment, the invention provides a bridging microfilter for coupling to a ring line and tip line of a POTS/xDSL shared carrier in detection of voice traffic. The bridging microfilter includes a first differential mode inductor in series with a second differential mode inductor, first and second resistors in parallel with the first differential mode inductor, first and second capacitors in parallel with the second differential mode inductor, a first shunt leg interposed between the first and second differential mode inductors and coupled across the first and second differential mode inductors, and a second shunt leg coupled across the second differential mode inductor. The bridging microfilter has an impedance value of approximately 80 kxcexa9 or higher.
Further embodiments of the invention include apparatus and methods of varying scope.